The life span of red blood cells has been derived from the measurement of the clearance of Chromium 51 labelled red cells in vivo (Gray, S. J. and Stirling, K. 1950, J. Clin. Invest. 29: 1604-1613, for a review; Dacie and Lewis; Practical Haematology, Ninth Edition, 2001, Ed.; S. M. Lewis, B. J. Bain and I. Bates, Publ. Churchill Livingstone). This procedure is invasive and cumbersome and is not widely used. Other techniques have been developed to measure the life span of erythrocytes non-invasively, including the measurement of carbon monoxide in breath (M. A. Virtue et al. 2004, Diabetes Care; vol. 27 No 4 pp 931-935), density centrifugation of red cells (Borun E R, et al. J Clin Invest 36:676, 1957) and flow cytometric measurement of CD35 on the cell surface of red cells (Lach-Trifilieff et al. 1999, Journal. Immunol. 162, (12): 7549). However, none of these techniques have been shown to consistently provide for the determination of life-span or mean age of red cells.
It is therefore desirable to develop systems and methods to determine the age of cellular hemoglobin and/or the mean age of red blood cells.